1927 medical helicopter transports were performed in Basle between 1986 and 1989. Of the total flights, 173 transports without patients and 186 incubator transports were excluded from the study. Treatment and transportation were provided for 1085 victims of trauma (70.2%) and 461 medical-surgical patients (29.8%), mostly with life-threatening conditions. 589 trauma patients were treated at the scene of accident and later transported by helicopter to a nearby medical center (54.3%). The 4.3% rate of negative emergency flights is low. Since introduction of the helicopter rescue system at Basle in 1975, scene flights have increased from 29% in 1984 to 46% in 1989. 47.4% of all patients were categorized as seriously ill or severely injured. 36.4% of all patients required intubation and assisted ventilation. Of the trauma patients, 54.3% involved scene-flights requiring in-field intensive therapy. Helicopter transport provides not only a rapid source of transportation, but also vital medical assistance at the scene of emergency. Transport generally occurs only after stabilization of vital functions. These factors contribute to the low mortality before return flights (3%) as well as during transport (0.3%). We conclude that early aggressive in-field intensive therapy can help to decrease both morbidity and mortality in emergency-care patients.